April 29, 2019 – Intermediate-Term Weather Report – Peak Nino 3.4 Index?

Written by Sig Silber

The pattern remains generally wet with a wide range of temperature anomalies due to unusually High Pressure developing in the Arctic. Both El Nino and the MJO are expected to ramp up over the next few weeks. Tomorrow we will get the official NOAA perspective on how this will play out for May. In tonight’s article, I discuss to some extent the current situation with respect to El Nino and the MJO and of course we provide the usual approximately thenty-five day forecast.

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Approaching Peak Nino 3.4

Here is a daily version of the Nino 3.4 Index.

But there could be boost to the El Nino

Recent CONUS Weather

Here is the recent history of the overall atmospheric pattern for North America and the North Pacific.

 And now looking at the recent weather.

And the 30 Days ending Aprill 20, 2019	And the 30 Days ending April 27, 2019
It is wetter especially in the Southeast and there are more warm anomalies	Not much change really. A bit wetter to the east.
Remember, these maps are a 30 average so the most distant seven days are removed and the most recent seven days are added.

Summary of the Forecast

We now provide our usual summary first for temperature and then for precipitation of small images of the four short-term maps. You can click on these maps to see larger versions. The easiest way to return to this report is by using the “Back Arrow” usually found top left corner of your screen to the left of the URL Box. Larger maps are available later in the article with the discussion and analysis.

Sometimes it is useful to see the evolution of the forecasts from the 1 – 5 Day, 6 – 10 Day (which NOAA considers to be Week-1 of their intermediate forecast) , 8 – 14 Day (which NOAA considers to be Week-2) and Week 3 and 4 (which after being issued overlap with Week-2). I do not have comparable maps for the Day 1 – 5 forecast in the same format as the three maps we generally work with. What I am showing for temperature is the Day 3 Maximum Temperature and for precipitation the five-day precipitation: the latter being fairly similar in format to the subsequent set of the maps I present each week but showing absolute QPF (inches of precipitation) not QPF deviation from Normal.

First Temperature

And then Precipitation

A. Now we will begin with our regular approach and focus on Alaska and CONUS (all U.S.. except Hawaii).

Water Vapor.

This view of the past 24 hours provides a lot of insight as to what is happening.

You can see from this animation that there is a Pacific Storm arriving. There is also moisture entering Texas from the Pacific via Mexico.

Tonight, Monday April 29, 2019, as I am looking at the above graphic, you see very little moisture impacting the West Coast. There is some moisture entering Texas via Mexico. There is activity over the Rockies and the Plains States from earlier storms. There is another wave of moisture ready to arrive.

We now discuss Atmospheric Rivers i.e. thick concentrated movements of water moisture. More explanation on Atmospheric Rivers can be found by clicking here or if you want more theoretical information by clicking here. The idea is that we have now concluded that moisture often moves via narrow but deep channels in the atmosphere (especially when the source of the moisture is over water) rather than being very spread out. This raises the potential for extreme precipitation events. You can convert this graphic into a flexible forecasting tool by clicking here. One can obtain views of different geographical areas by clicking here.

The graphic we had been using was not updating so for the time being we added another version which is updating. It does not cover all of CONUS but it does provide a very good view of what is happening in the Pacific and the North American West Coast. But the original graphic we were using is not working so we are using both.

And this graphic provides a better view of all of CONUS.

I have decided to include the IWT information for Europe.

And Now the Day One and Two CONUS Forecasts (These graphics have recently been revised by NOAA and I think greatly improved).

Day One CONUS Forecast	Day Two CONUS Forecast
These graphics update and can be clicked on to enlarge but my brief comments are only applicable to what I see on Monday night prior to publishing.
We no longer see snow. We see more convective activity.

Additional useful forecasts are available from our Severe Weather Report which this week can be found here and always can be located via this directory.

60 Hour Forecast Animation

Here is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at links provided below. The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.

The below makes it easier to focus on a particular day.  The best way to read them is from left to right on the first row and then from left to right in the row below it.

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What is Behind the Forecasts? Let us try to understand what NOAA is looking at when they issue these forecasts.

Below is a graphic which highlights the forecast surface Highs and the Lows re air pressure on Day 7. The Day 3 forecast can be found here. the Day 6 Forecast can be found here.

The weak Aleutian Low with surface central pressure of 992 hPa is forecast on Day 7 to be in the Bering Sea and not at all in the Gulf of Alaska. There is an Arctic High with surface central pressure of 1032 hPa and it actually extends to the Hawaiian High which in the Pacfic has  surface central pressure of 1020 hPa. The clockwise circulation of a High centered on Southeast with surface central pressure of 1016 hPa may bring Gulf of Mexico moisture into the Great Plains. We again see a dry line on the map between NM And Texas which should have a lot of convective activity and we see an inverted trough in the Sea of Cortez extending into the Southwest almost like what we see during the Monsoon. There is a high over Mexico with surface central pressure of 1012 hPa which again is much like the lead-up to the North American Monsoon.

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Looking at the current activity of the Jet Stream. The below graphics and the above graphics are very related.

Not all weather is controlled by the Jet Stream (which is a high altitude phenomenon) but it does play a major role in steering storm systems especially in the winter The sub-Jet Stream level intensity winds shown by the vectors in this graphic are also very important in understanding the impacts north and south of the Jet Stream which is the higher-speed part of the wind circulation and is shown in gray on this map. In some cases however a Low-Pressure System becomes separated or “cut off” from the Jet Stream. In that case it’s movements may be more difficult to predict until that disturbance is again recaptured by the Jet Stream. This usually is more significant for the lower half of CONUS with the cutoff lows being further south than the Jet Stream. Some basic information on how to interpret the impact of jet streams on weather can be found here and here. I have not provided the ability to click to get larger images as I believe the smaller images shown are easy to read.

Current	Day 5
You can see the current pattern here. It is north and you can see that little trough over Montana	The pattern is forecast to shift east. It is still north. The Trough is forecast to impact the Great Lakes area.

Putting the Jet Stream into Motion and Looking Forward a Few Days Also

To see how the pattern is projected to evolve, please click here. In addition to the shaded areas which show an interpretation of the Jet Stream, one can also see the wind vectors (arrows) at the 300 Mb level.

This longer animation shows how the jet stream is crossing the Pacific and when it reaches the U.S. West Coast is going every which way.

Click here to gain access to a very flexible computer graphic. You can adjust what is being displayed by clicking on “earth” adjusting the parameters and then clicking again on “earth” to remove the menu. Right now it is set up to show the 500 hPa wind patterns which is the main way of looking at synoptic weather patterns. This amazing graphic covers North and South America. It could be included in the Worldwide weather forecast section of this report but it is useful here re understanding the wind circulation patterns.

500 MB Mid-Atmosphere View

The map below is the mid-atmosphere 7-Day chart rather than the surface highs and lows and weather features. In some cases it provides a clearer less confusing picture as it shows only the major pressure gradients. This graphic auto-updates so when you look at it you will see NOAA’s latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot. Thinking about clockwise movements around High Pressure Systems and counterclockwise movements around Low Pressure Systems provides a lot of information.

Here is the whole suite of similar maps for Days 3, 4, 5, 6 and repeated for Day 7. It is quite complicated. Read from left to right first  row and then left to right on the  second row. 

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Here is the seven-day cumulative precipitation forecast. More information on how to interpret this graphic is available here.

Four – Week Outlook: Looking Beyond Days 1 to 5, What is the Forecast for the Following Three + Weeks?

I use “EC” in my discussions although NOAA sometimes uses “EC” (Equal Chances) and sometimes uses “N” (Normal) to pretty much indicate the same thing although “N” may be more definitive.

First – Temperature

6 – 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on April 29, 2019 was 4 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on April 29, 2019 was 4 out of 5).

–

Looking further out.

Now – Precipitation

6 – 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on April 29, 2019 was 4 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on April 29, 2019 was 4 out of 5)

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today April 29, 2019

6-10 DAY OUTLOOK FOR MAY 05 – 09 2019  

Today’s ensemble mean solutions from the GEFS, ECMWF, and the Canadian all show positive height anomalies over the Polar regions in the 6-10 day period corresponding to a negative phase of the Arctic Oscillation. This is turn allows an amplified pattern to take shape over the mid-latitudes, which is highlighted in the GEFS and ECMWF ensembles, and less so in the Canadian ensembles. Ridging and above normal height anomalies are forecast for the East and troughing and negative height anomalies are forecast for the West. Upstream, ridging is favored over the Alaskan mainland and the Northeastern Pacific, with troughing forecast over the Bering Sea. Troughing and negative height anomalies are forecast over the North Atlantic in conjunction with a negative phase of the North Atlantic Oscillation, which may limit the northward extension of the ridge over the Eastern CONUS.

Ridging over the Eastern CONUS favors above normal temperature probabilities for the Central and Southern Plains eastward through the Southeast and mid-Atlantic. Near to below normal heights over the North Atlantic favor relatively cooler temperatures for parts of New England. Development of troughing favors near normal or below normal temperature probabilities for parts of the Northern Plains, Northern Rockies, and the Southwest. The influence of the Northeastern Pacific ridge favors above normal temperature probabilities for the Pacific Northwest. Above normal temperature probabilities are highlighted for the Aleutians and Western and Northern mainland Alaska due to the influence of ridging and southerly flow.  

The overall set-up favors increased chances of above normal precipitation across  much of the country, particularly over the Desert Southwest and the Mississippi Valley. Shortwave energy is forecast to move into Southern California early in the period, favoring above normal precipitation probabilities over areas that are normally rather dry. This same energy is forecast to propagate further inland, where interaction with moist air in place over the Plains and  Mississippi Valley results in the development of heavy rain. Both the GEFS and ECMWF ensembles show upwards of 2 inches of rain for the period, with higher amounts shown in deterministic runs. Flooding concerns will likely be exasperated as this heavy rain would potentially occur over already saturated areas. Ridging over the Northeastern Pacific favors below normal precipitation probabilities for the Pacific Northwest. Southerly flow across Alaska results in a tilt toward above normal precipitation probabilities for most of the state, especially the Aleutians and southwestern mainland. The exceptions being parts of northern mainland Alaska and the Panhandle where below normal probabilities are favored.

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Above average, 4 out of 5, due to good agreement among available models and tools.  

8-14 DAY OUTLOOK FOR MAY 07 – 13 2019 

The 6-10 day pattern is forecast to persist throughout week-2 with minimal differences in the forecast relative to the 6-10 day period. Troughing and below normal temperature probabilities continue to be favored over parts of the Southwest, the Rockies, and the Northern Plains. Ridging and above normal temperature probabilities are favored for the East. The Madden Julian Oscillation is forecast to propagate into phase 6 in the week-2 period, which further supports above normal temperatures in the East. Above normal temperatures probabilities are also highlighted for the West Coast, along with Alaska.

Above normal precipitation probabilities remain for the Plains and Mississippi Valley where the baroclinic zone between the warmth in the East and relatively cooler conditions in the West will continue to be a focus for precipitation enhancement. Dynamical guidance supports several inches of rain during this period. Troughing continues to favor increased precipitation chances over the Southwest. Below normal precipitation is forecast for the Pacific Northwest and the Alaska Panhandle, and above normal precipitation is highlighted for the remainder of Alaska.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Above average, 4 out of 5, due to persistence of amplified pattern in week-2.

The next set of long-lead monthly and seasonal outlooks will be released on May 16.

Analogs to the NOAA 6 – 14 Day Outlook.

Now let us take a detailed look at the “Analogs”.

NOAA normally provides two sets of Analogs.

A. Analogs related to the 5 day period centered on 3 days ago and the 7 day period centered on 4 days ago. “Analog” means that the weather pattern then resembles the recent weather pattern and the recent pattern is used to initialize the models to predict the 6 – 14 day Outlook.

B. There is a second set of analogs associated with the Outlook. It compares the forecast (rather than the prior period) to past weather patterns. I have not been regularly analyzing this second set of information. The first set applies to the 5 and 7 day observed pattern prior to today. The second set relates to the correlation of the forecasted outlook 6 – 10 days out and 8 – 14 days out with similar patterns that have occurred in the past during a longer period that includes the dates covered by the 6 – 10 Day and 8 – 14 Day Outlook. The second set of analogs also has useful information as it indicates that the forecast is feasible in the sense that something like it has happened before. I am not very impressed with that approach. But in some ways both Approach A and B are somewhat similar. I conclude that if the Ocean Condition now are different then the analogs and if the state of ENSO now is different than the analogs that is a reason to have increased lack of confidence in the forecasts and vice versa.

They put the first set of analogs in the discussion with the second set available by a link so I am assuming that the first set of analogs is the most meaningful and I find it so. But NOAA prefers the first set (A) as it helps them (or at least they think it does) assess the quality of the forecast.

Here are today’s analogs in chronological order although this information is also available with the analog dates listed by the level of correlation. I find the chronological order easier for me to work with. It also helps the reader see the impact of the phases of the PDO and AMO which are shown. The first set (A) which is what I am using today applies to the 5 and 7 day observed pattern prior to today.

* I assign values that are consistent with the trend so I am doing some subjective smoothing with respect to the Phases of the AMO and PDO shown in this table. (t) = a month where the Ocean Cycle Index has just changed from a consistent pattern or does change the following month to a consistent pattern.

The spread among the analogs from April 16 to May 6 is 20 days which is a very tight spread and may suggest a pattern that is easier to forecast. I have not calculated the centroid of this distribution which would be the better way to look at things but the midpoint, which is a lot easier to calculate, and fairly accurate if the dates are reasonably evenly distributed, is about April 26, 2019. These analogs are describing historical weather that was centered on 3 days and 4 days ago (April 25 or April 26). So the analogs could be considered to be a in sync with respect to weather that we would normally be getting right now.

For more information on Analogs see discussion in the GEI Weather Page Glossary. For sure it is a rough measure as there are so many historical patterns but not enough to be a perfect match with current conditions. I use it mainly to see how our current conditions match against somewhat similar patterns and the ocean phases that prevailed during those prior patterns. If everything lines up I have my own measure of confidence in the NOAA forecast. Similar initial conditions should lead to similar weather. I am a mathematician so that is how I think about models.

Including duplicates, there are five Neutral analogs, two El Nino Analogs, and three La Nina Analogs. This suggests that El Nino may not right now have much impact on the weather pattern for CONUS and Alaska. The pre-forecast analogs this week are most supportive of McCabe D which is “Southwest Drought extending to the North and also the Great Lakes” and least supportive of McCabe A which is “Very Little Drought, Southern Tier and Northern Tier from the Dakotas east wet. Some Drought on East Coast”. By being most supportive of McCabe D and least supportive of McCabe A, the analogs are somewhat in conflict with the NOAA 6 – 14 Day Forecast and are suggesting the Southwest may be less wet than forecast. The analogs are certainly not able to take into account the MJO which is over the Maritime Continent not in the part of the Pacific which is not the basis for the selection of the analogs. And the analogs today are mostly related to turning points in ENSO. So I do not know what to make of the contradiction between the analogs and the NOAA forecast. The analogs are not a very good predictor of weather. I do the analysis which also combines the phases of the AMO and PDO to see if it sheds additional light on the subject not as an alternative to the NOAA forecasts which are much more reliable. Sometimes they do add to the analysis but probably not tonight or at least I have not been able to decipher them.

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Historical Anomaly Analysis

When I see the same dates showing up often I find it interesting to consult this list.

A Useful Read

Some might find this analysis which you need to click to read interesting as the organization which prepares it focuses on the Pacific Ocean and looks at things from a very detailed perspective and their analysis provides a lot of information on the history and evolution of ENSO events.

Some Indices of Possible Interest: We should always remember that the forecast is driven by many factors some of which are conflicting in terms of their impacts. Please pay more attention to the graphics than my commentary which does not update on a regular basis once the article is published. The indices will continue to update. I provide these indices as they are important guidelines to the weather. It is in a way looking at the factors that are impacting the weather. There were developed because weather forecasters found them to be useful.

Eastern Pacific Oscillation. Here is a pretty good explanation. It is a bit like an extension further west of the AO.  Here is some history and five forecasts ranging from 4 days to 14 days. As you can see, we have been in the Negative or Cool Phase almost all winter. But this seems to have switched to the Warm Phase but now looks mostly neutral but starting off EPO Negative.

Here is another way of integrating all forecasts into a single graphic.  These forecasts extend out further into the future than the forecasts presented earlier. But they do not show the recent history.  Also the set of four does not include the AO but instead the WPO so  it is not the same but may be useful.

Madden Julian Oscillation (MJO)

The MJO is an area of convective activity along the Equator which circles the globe generally in 30 to 60 days. The location of the convective activity not only impacts the Equator but also the middle latitudes. Most people are not familiar with the MJO but at certain times it plays an important role Worldwide re weather and for CONUS.

This is the Summary from the weekly NOAA analysis of the MJO.

It is sometimes useful to look at the recent history of the MJO.

The MJO Index (more information can be found here) indicates where the MJO has been and this Hovmoeller Graphic shows this. The Index is show for the parts of the Equator where the MJO is most  usually found.

Forecast Models.

There are a lot of models and I try to read the results from all of them. For access to a variety of models, I refer readers here. This weekly report summarizes things. Here is another useful source of information.

Now the first of the two graphics we typically present which shows where the MJO is now and how it got there. 

This shows the recent history.  MJO is now in Phase 4. What next?

And then a forecast.  On this GFS graphic, the light gray shading shows the tracks which fit with 90% of the forecasts and the dark gray shading shows a smaller area that fits with 50% of the forecasts The large dot is the current location.

* Remember when clicking on an image to enlarge does not work, usually it will work to right click with your mouse and click on “view image”. Sometimes it just does not work when I set it up to enlarge by simply clicking on the image.

Here is a larger version of the graphic on the left

 We showed this earlier

B. Beyond Alaska and CONUS Let’s Look at the World which of course also includes Alaska and CONUS

It is Useful to Understand the Semipermanent Pattern that Control our Weather and Consider how These Change from Winter to Summer. These two graphics (click on each one to enlarge) are from a much larger set available from the Weather Channel. They highlight the position of the Bermuda High which they are calling the Azores High in the January graphic and is often called NASH and it has a very big impact on CONUS Southeast weather and also the Southwest. You also see the north/south migration of the Pacific High which also has many names and which is extremely important for CONUS weather and it also shows the change of location of the ITCZ which I think is key to understanding the Indian Monsoon. A lot of things become much clearer when you understand these semi-permanent features some of which have cycles within the year, longer period cycles and may be impacted by Global Warming. We are now moving into Early- to Mid-May. We should be returning from the set of positions shown below for the Winter Pattern to the Summer Pattern. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant.

World Forecasts

1. Today (Source: University of Maine)

2. Short-term set for day six but can be adjusted (BOM – Australia)

3. 8 – 14 Day (NOAA/Canada/Mexico Experimental NAEFS))

4 Tropical  Activity

1.  Forecast for Today (you can click on the maps to enlarge them)

And now precipitation

Additional Maps showing different weather variables can be found here.

2. Forecast for Day 6 (Currently Set for Day 6 but the reader can change that)

World Weather Forecast produced by the Australian Bureau of Meteorology. Unfortunately I do not know how to extract the control panel and embed it into my report so that you could use the tool within my report. But if you visit it Click Here and you will be able to use the tool to view temperature or many other things for THE WORLD. It can forecast out for a week. Pretty cool. Return to this report by using the “Back Arrow” usually found top left corner of your screen to the left of the URL Box. It may require hitting it a few times depending on how deep you are into the BOM tool. Below are the current worldwide precipitation and temperature forecasts for six days out. They will auto-update and be current for Day 6 whenever you view them. If you want the forecast for a different day Click Here

Again, please remember this graphic updates every six hours so the diurnal pattern can confuse the reader.

Now Precipitation

3. And now we have experimental 8 – 14 Day World forecasts from the NAEFS Model.

First Temperature

Then Precipitation

4. Tropical Hazards.

C. ENSO SUMMARY of Current Status. 

This section is organized into three parts.

1. Current Sea Surface Temperatures (SST)

2. Current Nino 3.4 Readings

3. The Surface Air Pressure Pattern that confirms the state of ENSO.

1. Current and Recent Sea Surface Temperatures (SST)

A major driver of weather is Surface Ocean Temperatures. Evaporation only occurs from the Surface of Water. So we are very interested in the temperatures of water especially when these temperatures deviate from seasonal norms thus creating an anomaly. The geographical distribution of the anomalies is very important. To a substantial extent, the temperature anomalies along the Equator have disproportionate impact on weather so we study them intensely and that is what the ENSO (El Nino – Southern Oscillation) cycle is all about. Subsurface water can be thought of as the future surface temperatures. They may have only indirect impacts on current weather but they have major impacts on future weather by changing the temperature of the water surface. Winds and Convection (evaporation forming clouds) is weather and is a result of the Phases of ENSO and also a feedback loop that perpetuates the current Phase of ENSO or changes it. That is why we monitor winds and convection along or near the Equator especially the Equator in the Eastern Pacific.

My focus here is sea surface temperature anomalies as they are one of the two largest factors determining weather around the World. If we want to have a good feel for future weather, we need to look at the oceans as our weather mostly comes from oceans and we need to look at surface temperature anomalies (weather develops from the ocean surface

It is the ocean surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. So we are interested in the actual ocean surface temperatures and the departure from seasonal normal temperatures which is called “departures” or “anomalies”. Since warm water facilitates evaporation which results in cloud convection, the pattern of SST anomalies suggests how the weather pattern east of the anomalies will be different than normal.

Current Sea Surface Temperature (SST) Departures from Normal for this Time of the Year i.e. Anomalies

First the categorization of the current Monthly Average SST anomalies.
The Mediterranean, Black Sea and Caspian Sea	Western Pacific	West of North America	North and East of North America	North Atlantic
The Mediterranean is Neutral. The Black Sea is warm and the Caspian Sea is very slightly warm.	Mixed	Waters in Bristol Bay are warm. Warm off Baja and out to sea	Great Lakes cool Waters offshore of East Coast slightly cool to the north and slightly warm to the south.. .	Slightly warm Cool south of Greenland
Equator	Eastern Pacific Slightly Warm.
Africa	West of Australia	North, South, and East of Australia	West of South America	East of South America
Mixed south and southwest of Africa Warm east of Madagascar	Neutral	Warm Southeast to and beyond New Zealand Cool SSW	Neutral	Warm 10S to 30S and out to sea. Cool 50S to Cape Horn.

Then we look at the change in the anomalies. The SST anomaly is sort of like the first derivative and the change in the anomaly is somewhat like a second derivative. It tells us if the anomaly is becoming more or less intense.

I am only showing the currently issued version of the NINO SST Index Table as the prior values are shown in the small graphics on the right with this graphic. The same data in graphic form but going back a couple of more years can be found here. The full table of values can be found here. NOAA considers Nino 3.4 shown in the graphic as the best indicator of Equatorial Surface Temperature Anomalies associated with different phases of ENSO. There is a duration requirement to be a recorded El Nino or La Nina but to have El Nino Conditions the Nino 3.4 index needs to be +0.5C or warmer and to have La Nina Conditions the Nino 3.4 Index needs to be -0.5C or cooler.

ENSO Update.

The computer models are more enthusiastic than the meteorologists and the two forecasts are shown below

Early April Meteorologist Survey	Mid-April Analysis of Model Forecasts

Also published on April 18 was the plume of forecasts from a variety of models. These are forecasts of the Nino 3.4 Index.

This graphic brings the Nino 3.4 up to date and is easy to read.

Here is a daily version

Starting with Surface Conditions.

TAO/TRITON GRAPHIC (a good way of viewing data related to the part of the Equator and the waters close to the Equator in the Eastern Pacific where we monitor to determining the current phase of ENSO. It is probably not necessary to follow the discussion below, but here is a link to TAO/TRITON terminology.

And here is the current version of the TAO/TRITON Graphic. The top part shows the actual temperatures, the bottom part shows the anomalies i.e. the deviation from normal.

This may help put the above graphics in focus.

The following graphic is some similar to the above but it updates every five days not once per week. The date shown is the midpoint for the five-day average. It shows a lot more detail than the above graphic. You can see some water at depth that is very anomalously warm.

3. The Surface Air Pressure that Confirms the Nino 3.4 Index

And of course, Queensland Australia is the official keeper of the SOI measurements.

SOI = 10 X [ Pdiff – Pdiffav ]/ SD(Pdiff) where Pdiff = (average Tahiti MSLP for the month) – (average Darwin MSLP for the month), Pdiffav = long term average of Pdiff for the month in question, and SD(Pdiff) = long term standard deviation of Pdiff for the month in question. So really it is comparing the extent to which Tahiti is more cloudy than Darwin, Australia. During El Nino we expect Darwin Australia to have lower air pressure and more convection than Tahiti (Negative SOI especially lower than -7 correlates with El Nino Conditions). During La Nina we expect the Warm Pool to be further east resulting in Positive SOI values greater than +7).

D. Putting it all Together.

At this time, La Nina Conditions along the Equator have come to an end and we are slowly entering into weak El Nino Conditions.

There is some thought now that we might have a marginal El Nino situation that extends into next Winter. JAMSTEC ruled that out but there are some signs that this could happen.  All El Nino forecasting right now runs up against the Spring Prediction Barrier (SPB) and forecasts in May are far more reliable.

E. Relevant Recent Articles and Reports

Weather in the News

Nothing to report

Weather Research in the News

Nothing to report

Global Warming in the News

Nothing to report

Useful Reference Information

Understand How the Jet Stream Impacts Weather

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Standard Pressure Levels

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